feat: add format and metadata filters to books page

Add two new filters to the books listing page:
- Format filter (CBZ/CBR/PDF/EPUB) using existing API support
- Metadata linked/unlinked filter with new API support via
  LEFT JOIN on external_metadata_links (using DISTINCT ON CTE
  matching the series endpoint pattern)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/backoffice/app/books/page.tsx

@@ -18,6 +18,8 @@ export default async function BooksPage({
   const libraryId = typeof searchParamsAwaited.library === "string" ? searchParamsAwaited.library : undefined;
   const searchQuery = typeof searchParamsAwaited.q === "string" ? searchParamsAwaited.q : "";
   const readingStatus = typeof searchParamsAwaited.status === "string" ? searchParamsAwaited.status : undefined;
+  const format = typeof searchParamsAwaited.format === "string" ? searchParamsAwaited.format : undefined;
+  const metadataProvider = typeof searchParamsAwaited.metadata === "string" ? searchParamsAwaited.metadata : undefined;
   const sort = typeof searchParamsAwaited.sort === "string" ? searchParamsAwaited.sort : undefined;
   const page = typeof searchParamsAwaited.page === "string" ? parseInt(searchParamsAwaited.page) : 1;
   const limit = typeof searchParamsAwaited.limit === "string" ? parseInt(searchParamsAwaited.limit) : 20;
@@ -62,7 +64,7 @@ export default async function BooksPage({
       totalHits = searchResponse.estimated_total_hits;
     }
   } else {
-    const booksPage = await fetchBooks(libraryId, undefined, page, limit, readingStatus, sort).catch(() => ({
+    const booksPage = await fetchBooks(libraryId, undefined, page, limit, readingStatus, sort, undefined, format, metadataProvider).catch(() => ({
       items: [] as BookDto[],
       total: 0,
       page: 1,
@@ -91,12 +93,26 @@ export default async function BooksPage({
     { value: "read", label: t("status.read") },
   ];
 
+  const formatOptions = [
+    { value: "", label: t("books.allFormats") },
+    { value: "cbz", label: "CBZ" },
+    { value: "cbr", label: "CBR" },
+    { value: "pdf", label: "PDF" },
+    { value: "epub", label: "EPUB" },
+  ];
+
+  const metadataOptions = [
+    { value: "", label: t("series.metadataAll") },
+    { value: "linked", label: t("series.metadataLinked") },
+    { value: "unlinked", label: t("series.metadataUnlinked") },
+  ];
+
   const sortOptions = [
     { value: "", label: t("books.sortTitle") },
     { value: "latest", label: t("books.sortLatest") },
   ];
 
-  const hasFilters = searchQuery || libraryId || readingStatus || sort;
+  const hasFilters = searchQuery || libraryId || readingStatus || format || metadataProvider || sort;
 
   return (
     <>
@@ -117,6 +133,8 @@ export default async function BooksPage({
               { name: "q", type: "text", label: t("common.search"), placeholder: t("books.searchPlaceholder") },
               { name: "library", type: "select", label: t("books.library"), options: libraryOptions },
               { name: "status", type: "select", label: t("books.status"), options: statusOptions },
+              { name: "format", type: "select", label: t("books.format"), options: formatOptions },
+              { name: "metadata", type: "select", label: t("series.metadata"), options: metadataOptions },
               { name: "sort", type: "select", label: t("books.sort"), options: sortOptions },
             ]}
           />

apps/backoffice/app/components/LiveSearchForm.tsx

@@ -18,6 +18,10 @@ const FILTER_ICONS: Record<string, string> = {
   metadata_provider: "M7 7h.01M7 3h5c.512 0 1.024.195 1.414.586l7 7a2 2 0 010 2.828l-7 7a2 2 0 01-2.828 0l-7-7A1.994 1.994 0 013 12V7a4 4 0 014-4z",
   // Sort - arrows up/down
   sort: "M3 4h13M3 8h9m-9 4h6m4 0l4-4m0 0l4 4m-4-4v12",
+  // Format - document/file
+  format: "M7 21h10a2 2 0 002-2V9.414a1 1 0 00-.293-.707l-5.414-5.414A1 1 0 0012.586 3H7a2 2 0 00-2 2v14a2 2 0 002 2z",
+  // Metadata - link/chain
+  metadata: "M13.828 10.172a4 4 0 00-5.656 0l-4 4a4 4 0 105.656 5.656l1.102-1.101m-.758-4.899a4 4 0 005.656 0l4-4a4 4 0 00-5.656-5.656l-1.1 1.1",
 };
 
 interface FieldDef {